Summary Knee osteoarthritis (OA) is a prevalent chronic degenerative disease that is a primary cause of mobility disability among older adults in the U.S. Obesity is a primary modifiable risk factor for the progression of symptomatic knee OA that is associated with increased pain and an increased risk of functional limitations. It is widel accepted that Exercise (EX) is a safe, efficacious lifestyle intervention that consistently yields clinically meaningful improvements in relevant knee OA outcomes. Although EX is a cornerstone of the Arthritis Foundation's (AF) community-based self-management programs, lifestyle interventions combining Exercise and Dietary Weight Loss (EX+DWL) has yielded more favorable change in mobility performance, pain, and weight loss relative to either EX or DWL alone in older overweight knee OA patients. Unfortunately, access to comprehensive weight management programs for overweight knee OA patients remains limited. From a translational perspective, effective community partnerships are needed to deliver widely accessible lifestyle interventions to prevent obesity and mobility disability in this population. Consequently, there is a critical need to determine the utility of delivering EX+DWL interventions in the community and to determine the comparable efficacy of this approach with those of traditional OA self-management programs currently available. Our overarching research goal is to develop efficacious and sustainable lifestyle interventions in health promotion and disease prevention efforts. Our objective in this application is to conduct a two-arm, 24 month randomized controlled trial, in collaboration with the Central Ohio AF, to determine the comparable efficacy of a community- based EX+DWL program versus the AF's Walk With Ease EX program which is now the focus of AF's self- management programming, in producing clinically meaningful improvements in relevant OA outcomes among older overweight or obese knee OA patients. Our central hypothesis is that the EX+DWL intervention will be a safe, efficacious approach that produces superior improvements in mobility disability and the secondary outcomes of weight loss, pain, and quality of life relative to the AF's Walk with Ease EX program. This hypothesis is formulated on the basis of our strong preliminary data demonstrating that the EX+DWL intervention proposed in this investigation yields meaningful improvements in these outcomes in knee OA patients as well as obese older adults at risk for mobility disability. At the completion o this project, we expect to have determined the comparative effectiveness of these two community-based interventions. In short, the primary positive impact of the proposed trial is that the results of this study could alter the AF's approach to the management of the functional consequences and symptoms of knee OA among older adults in communities nationwide.